Experimental evidence suggests that women (and left-handed people in general) have a less "differentiated" brain usage than men (and right-handed people in general). It seems that this whole Left vs. Right thing is much more fluid and variable from person to person than the "this bit does this, that bit does that" theory from last century implied. People born with hydrocephalus who have hardly any brain matter at all (less than 10% of what we normally have) can function perfectly normally, the body uses what it's got available - similarly people can recover from damage to one side of the brain and the other side can take over its functions.
I confess I've always been skeptical of the whole "this side's masculine, that side's feminine" interpretation - it seems to me to be an unconscious reinforcement of gender stereotypes, and some people seem suspiciously over-attached to the model.
But this is just based on stuff I've read and heard about the subject over the years since I first heard about the L/R brain theory - there's probably loads and loads of theories and counter-theories about it these days, even just in the interpretation of the data gathered.
